What I found is that written evidence for knocking on wood (and for the history of gesture as a whole) is remarkably sparse. In the Penguin Guide to Superstitions, folklorist Steve Roud offers a skeptical take on the provenance of knocking on wood due to the near total absence of written records about it:
new TextDecoder().decode(messageMemoryView);。关于这个话题，雷电模拟器官方版本下载提供了深入分析
Who can get the chickenpox vaccine on the NHS?，更多细节参见91视频
IST — 7 p.m.，这一点在搜狗输入法下载中也有详细论述